NEW YORK (Reuters)
— Strength training,
traditionally favored by body builders seeking to bulk up, has
become the go-to regimen for athletes, weekend warriors and exercise
enthusiasts determined to slim down.

Fitness experts say metabolic strength training, a
high-intensity, full-body interval workout, can add definition to
the shape of runners, cyclists and other cardio devotees willing to
put some muscle into it.

Florida-based trainer Nick Tumminello believes strength training
should be the primary form of exercise for everyone except
beginners.

While traditional strength training uses free weights or weight
machine to build endurance and muscles, metabolic strength training
combines high-intensity interval circuits with changing combinations
and repetitions using free weights, kettlebells, barbells, dumbbells
and resistance bands to increase the metabolic rate after and during
the workout.

"The body-building model is great for maximizing body building, but
for the average individual looking for fat loss, or to feel better,
or to improve general fitness, this creates more of a metabolic
disturbance," he said.

Because the combinations are intense, Tumminello recommends starting
at once or twice a week and building up gradually to three or four
times.

"You do need recovery time," he said, adding that too many beginners
tend to take an all-or-nothing approach. "Try to set a realistic
goal."

Jenn Burke, a San Francisco-based personal trainer and fitness
manager at Crunch, a national chain of gyms, said that steady
cardiovascular activity, such as running or cycling, is great for
burning lots of calories at a time and increasing heart rate and
lung capacity.

But unlike cardio activity, strength training will continue to burn
calories up to 72 hours after the exercise is over through a
phenomenon called after-burn.

Modern strength training, she said, is less about how much weight
you can lift than it is about how to make the body more efficient,
lean, toned and strong.

"Strength training is about the quality of life," Burke said. "You
can be skinny but not have the ability to lift your suitcase."

Although research has shown people cannot spot reduce, such as
targeting just the thighs or arms for slimming, Burke said it is
possible to enhance an area of the body with strength training.

"Men are generally drawn to body building seeking size or
presence," she said. "Women come for toned and sculpted arms, legs
and butts."

Muscle strength, increased bone mineral density and increased
strength in the connective tissues or tendons and ligaments are
among the benefits of strength training, according to Jacque
Ratliff, an exercise physiologist with the American Council on
Exercise.

"If someone falls, the more strength in their muscles, bones,
tendons, ligaments, the less likely they are to be injured," Ratliff
said.

Strength training also promotes elasticity in muscle.

"Generally, people want to tone up, to become leaner so the muscles
are more defined," she said. "Muscular tone from a biomechanical
aspect is the ability of muscles and connective tissue to hold the
body in position."

The more muscle mass we have, she added, the higher the metabolism
at rest.

The American Council on Exercise recommends a minimum of one to two
days of strength training per week, Ratliff said, but she cautions
that metabolic strength training is a high intensity activity that
needs to be monitored and programmed correctly to avoid injury.

"This is not something you would start someone on who is very new to
exercising," she said.